Al-Ti Oxide Research Articles

Tannic acid mediated coating of Al-Ti-oxide nanolayer on LiCoO2 cathode for high-voltage lithium-ion batteries

High-voltage LiCoO2 (LCO) satisfies the demand of high-energy lithium-ion batteries, but suffers adverse factors including structural irreversibility, micro-crack formation, active material erosion and electrode/electrolyte side reactions, which limits its electrochemical performance beyond 4.2 V. Here, we employed a surface coating method based on tannic acid (TA) pretreatment to vary the properties of LCO surface. The TA-mediated Al-Ti oxide (ATO) coating on LCO resulted in the interface doping of Al3+ and Ti4+ as well as the spinel phase transition layer, which inhibited the surface degradation and the structural instability. As a result, the obtained PLCO@ATO0.5% maintained 112 mAh g−1 after 600 cycles with a high voltage of 4.5 V. It also exhibited capacity retention of 80% after 100 cycles at 45 °C and the rate performance of 155 mAh g−1 at 10 C.

Improving the high-rate performance of LCO cathode by metal oxide coating: Evaluation using single particle measurement

Surface coating is a key approach for lithium-ion batteries (LIBs) to improve the high-rate performance and stability of batteries. LiCoO2 (LCO) has been one of the promising cathode materials in LIBs due to its high theoretical capacity of 274 mAh/g and high theoretical density (5.1 g cm−3) of material. However, the capacity used is only 140 mAh/g (∼50 % of theoretical capacity) under the voltage condition limited to 4.2 V. Increasing the operation voltage is the prime way to increase the energy density of the LCO electrode. In this study, we synthesize the pristine and Al-Ti oxide coated LCO materials by simple, cost-effective and eco-friendly sol–gel method and its intrinsic parameters are measured by single particle measurement (SPM) technique. A quantitative evaluation of the electrochemical properties of the active material shows a clear difference between pristine LCO and Al-Ti@ LCO. The measured rate characteristics show that Al-Ti@ LCO has higher discharge capacity under the same current rate condition and stable cycling ability. The high voltage rate capability of LCO is exponentially increased with Al-Ti oxide coating with the highest retention of 96 % after 50 cycles within 3.0–4.5 V at 4.2C. From Tafel plot analysis the charge transfer resistance (RCT) of Al-Ti@ LCO was lower in all DOD states than pristine LCO. Also, to investigate mass transfer properties, GITT was carried out. The Al-Ti oxide coating is believed to make the LCO electrode more resistant to interfacial side reactions and fast structural degradation at high voltage and thus reduce the degradation of active material within long cycling. This result shows Al-Ti oxide coating layer contributes to the enhancement of electrochemical performance without interfering with lithium-ion diffusion.

Phosphate Adsorption onto an Al-Ti Bimetal Oxide Composite in Neutral Aqueous Solution: Performance and Thermodynamics

Phosphorus (P) pollution and phosphorus recovery are important issues in the field of environmental science. In this work, a novel Al-Ti bimetal composite sorbent was developed via a cost-effective co-precipitation approach for P removal from water. The adsorptive performance and characteristics of P onto Al-Ti sorbent were evaluated by batch adsorption experiments. The effects of Al:Ti molar ratio, initial P concentration and reaction temperature were investigated. The microstructural characteristics of the Al-Ti sorbent were confirmed by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, and nitrogen adsorption-desorption measurements. Kinetic studies showed that the adsorption of P on Al-Ti oxide proceeds according to pseudo-second-order kinetics. The maximum adsorption capacity of phosphate on the Al-Ti oxide calculated from linear Langmuir models was 68.2 mg-P/g at pH 6.8. The Al-Ti oxide composite sorbent showed good potential for P recovery, owing to its large adsorption capacity and ease of regeneration.

Evolution of Al–Ti Oxide Inclusions in Fe-Based Alloys During Thermal Holding by a Novel Inductive Separation Method

Steelmaking has undergone significant technological advancements, particularly regarding oxide metallurgy. Herein, we employed a novel method of inductive separation for separating Al–Ti oxide from Ti-bearing oxides to trace the evolution of a specific type of oxide in a solid Fe-based alloy during thermal holding. The evolution occurred within the solid alloy; hence surface effects were prevented. The evolution was investigated at a lower temperature than what was used in previous studies; using this information, the impact of temperature was ascertained. The results revealed that, after holding for 0.5 hours at 1273 K, the shape of the Al–Ti oxide changed from spherical to irregular. The homogeneous oxide changed to a heterogeneous oxide containing Al- and Ti-rich parts, and the compositional deviation became distinct after thermal holding. After 12 hours, the composition of the Al-rich parts approached that of Al2O3. A comparison of the variation of the Al–Ti oxide at 1273 K and 1573 K revealed that the ratio of the heterogeneous oxide increased at lower temperatures due to the greater degree of supersaturation of Al2O3. The mechanism involved the precipitation of Al2O3 from Al–Ti oxide during holding. The fundamental data on the time-dependent variation in the morphology and composition of the Al–Ti oxide function as a first step to modify the oxide using thermal holding to promote the induction of an intragranular acicular ferrite (IAF) microstructure.

Time-Dependent Evolution of Ti-Bearing Oxide Inclusions During Isothermal Holding at 1573 K (1300 °C)

Ti-bearing oxide inclusions are utilized to enhance the properties of steel used in shipbuilding, multi-purpose gas carriers, and pipelines in accordance with the principles of oxide metallurgy. Conventionally, Ti-bearing oxide inclusions have been assumed to be stable during isothermal holding. The authors propose the possibility of modifying Ti-bearing oxide inclusions by appropriate heat treatment. To provide fundamental information on the evolution of Ti-bearing inclusions in solid steel during isothermal holding, the effect of the isothermal holding time on their evolution at 1573 K (1300 °C) was studied systematically. For heterogeneous phase Al+Ti oxide in the as-cast alloys, the composition and size distribution were maintained during isothermal holding. In contrast, homogeneous phase Al-Ti oxide in the as-cast alloys changed to a heterogeneous oxide consisting of an Al-rich part and a Ti-rich part and its shape changed from spherical to irregular. The composition of the Al-Ti oxide changed upon isothermal holding for 0.5 hour, and it occurred earlier in the Al-Ti oxide with a higher Al content. The evolution mechanism is considered to involve the precipitation of Al2O3 from the Al-Ti oxide owing to crystallization of glassy oxide during isothermal holding. The results challenge the long-held opinion that Ti-bearing oxide inclusions are maintained in solid steel during isothermal holding, which is the first step toward modifying oxide inclusions by heat treatment as a new concept in oxide metallurgy.

Quantitative analysis of microstructure and impact toughness in the simulated coarse-grained heat-affected zone of Cu-bearing steels

ABSTRACTBecause of 0.32% Cu addition, the inclusion is modified from Al-Ti oxide covered with layer of MnS in Cu-free steel to Al-Ti oxide with shell of (Mn,Cu)S in Cu-bearing steel. The quantitative result reveals that the frequency of inclusion effectively for acicular ferrite nucleation, fraction of acicular ferrite and high angle grain boundary in the simulated coarse-grained heat-affected zone (CGHAZ) of Cu-bearing steel are higher than that of Cu-free steel, respectively. Therefore, the high density of acicular ferrite microstructures in CGHAZ of Cu-bearing steel with smaller crystallographic grain size has superior impact toughness than that in Cu-free steel.

Investigation on the formation mechanism of Ti-bearing non-metallic inclusions in Fe-Al-Ti-O-N alloy by inductive separation method

Formation mechanism of Ti-bearing non-metallic inclusions was studied by inductive separation method, and characterization method was selected according to the type of each inclusion. The Al+Ti oxide was heterogeneous consisting of Al2O3 with Ti rich oxide layer. Compositional and size distribution was characterized by automated SEM observation and EDS analysis. It is formed as the reduction of Al2O3 by Ti in molten alloy at 1873K. The Al-Ti oxide was homogenous. It was liquid at 1873K characterized by EBSD. The Al/Ti molar ratio of oxide was consistent with that in each alloy as analyzed by manual SEM/EDS analysis. Its formation mechanism is proposed to be the reaction among dissolved Ti, Al, and O in molten alloy at 1873K. TiN precipitated during solidification. The fraction of TiN smaller than 1μm was larger in alloy2 than that in alloy1 as analyzed by automated SEM/EDS analysis. It is resulted from larger supersaturation degree in alloy2 during solidification.

Evolution of Al-Ti Oxide Inclusion during Isothermal Heating of Fe-Al-Ti Alloy at 1573 K (1300 °C)

Evolution of Al-Ti oxide inclusion during 3 hour isothermal heating of Fe-Al-Ti alloy at 1573 K (1300 °C) was studied. Homogeneous spherical Al-Ti oxide inclusion with nonstoichiometric composition was observed in two as-cast alloys. After heating, most of the homogeneous Al-Ti oxide inclusions changed to heterogeneous ones with Al-rich and Ti-rich parts, while the remaining homogeneous oxides were rare in both alloys. The concentration gradient of Al and O was observed inside the heterogeneous inclusion. The size distribution extended more broadly, and the shape changed from spherical to irregular. The mechanism of the variation was proposed as the diffusion of Al and O in the homogeneous inclusion from the inside to the surface of inclusion to precipitate alumina during heating.

Striking activity enhancement of gold supported on Al-Ti mixed oxide by promotion with ceria in the reduction of NO with CO

The promotion of an Al-Ti mixed oxide supported gold catalyst (Au/AlTiOx) with ceria is shown to result in an unprecedented enhancement of its activity in the reduction of NO to N2 with CO. The parent Au/AlTiOx catalyst was prepared by depositing 3wt% gold on the mesoporous Al-Ti mixed oxide made by an evaporation-induced self-assembly (EISA) method using a triblock copolymer as a soft template. This parent Au/AlTiOx was impregnated with different loadings of CeOx resulting in molar ratios of Au:Ce in the catalysts of 4:1, 2:1 and 1:1. The deposited gold particles showed a relatively broad size distribution with maxima at 8–12nm, as evidenced by TEM. XRD and XPS analyses showed that the Al-Ti oxide support was made up of amorphous Al2O3-TiO2 mixed oxide and that the Ce component was present as a mixture of Ce3+ (Ce2O3) and Ce4+ (CeO2) partially covering the Au particles. The as-prepared catalysts were tested in the catalytic reduction of NO with CO in a continuous tubular microreactor at temperatures up to 300°C. The parent Au/AlTiOx catalyst showed very low activity (8.2% NO conversion at 300°C), whereas the ceria promoted catalyst containing a molar ratio of Au:Ce of 2:1 exhibited a dramatic enhancement of activity affording 100% NO conversion at the same conditions. The stability of this catalyst was tested in repetitive runs over 16h time-on-stream, which showed a slight loss of activity, while 100% selectivity to N2 was maintained. The spent catalyst could be easily regenerated reaching its original performance by heat treatment in flowing 5% O2/He.

Cu Atom Switch With Steep Time-to-ON-State Versus Switching Voltage Using Cu Ionization Control

To break the tradeoff relationship between fast and low-voltage programming of a Cu atom switch, the effect of the composition in the AlTi oxide buffer layer placed on a Cu electrode is investigated. To improve the voltage dependence of time-to-ON-state, namely, switching slope (SS), the Cu ionization rate is increased by changing the composition ratio of the AlTi oxide buffer. An Al0.5Ti0.5O y buffer leads to an extremely steep SS of 56 mV/decade by eliminating metallic Al residue on the Cu electrode. This buffer enables fast (10 ns) and low-voltage ( $\sim 2$ V) programming, as demonstrated in a 1-Mbit array. Cycle endurance ( $> 10^{3}$ cycles) with a high ON/OFF resistance ratio ( $> 10^{4})$ was also confirmed. The steep SS technology is indispensable for conducting bridges used in a low-power nonvolatile field-programmable gate array.

Titanium-doped alumina for catalytic dehydration of methanol to dimethyl ether at relatively low temperatures

Mesoporous Al–Ti oxide composites with molar %Ti of 3, 5, 10, and 20 as well as pure γ-alumina were prepared using a template-free sol–gel method in the absence of a catalyst. The prepared composites were characterized by powder XRD, FTIR spectroscopy and N 2 adsorption for BET surface area and porosity measurements. The composites and the pure alumina possessed relatively high surface areas, 350–410 m 2/g, and high porosities after calcination at 500 °C. FTIR spectroscopy was employed to study the products of the catalytic dehydration of methanol to dimethyl ether, DME, over the prepared catalysts at reaction temperatures between 180 and 300 °C. Compared with pure γ-alumina, the Ti-modified alumina with %Ti < 10 showed higher catalytic activity in the methanol dehydration and better selectivity to DME. Composites with %Ti of 3 and 5 showed the highest activity at relatively lower temperatures than the other catalysts where they showed their highest activity at 190 and 200 °C, respectively. The activity of all studied catalysts slightly decreased as the temperature was raised to 300 °C and dropped considerably when the temperature was decreased to 180 °C. However, the activity of Al–Ti-3 dropped only slightly at both temperatures. The selectivity to DME was dependent on the reaction temperature where 100% DME selectivity was obtained at temperatures ⩽220 °C and as the temperature was raised to 300 °C, some CH 4 and CO 2 formed on the account of DME.

Formation and Evolution of Al–Ti Oxide Inclusions during Secondary Steel Refining

The process of Al deoxidation and Ti alloying during RH degassing treatment was studied under an Ar atmosphere at secondary steelmaking temperature (1600—1650°C) in an induction furnace equipped with an oxygen probe and a steel sampler. The formation of inclusions during partial Al deoxidation and Ti addition, and the reduction of Ti–Al–O inclusions by second Al addition are discussed using thermodynamic calculations. Specific attention is given to inclusion size and the compositional relation between the inclusions and the steel. The combination of experimental and calculated results shows that, in order to prevent Ti oxidation in liquid steel, it is essential to control [Al] in liquid steel to a level of approximately 200 ppm prior to Ti addition to achieve around 500 ppm [Ti] with minimal Ti loss during the alloying process.

Modification of Nanostructured TiO2 Electrodes by Electrochemical Al3+ Insertion: Effects on Dye-Sensitized Solar Cell Performance

Nanostructured TiO2 films were modified by insertion with Al ions using an electrochem. process. After heat treatment these films were suitable as electrodes in dye-sensitized solar cells. By a catechol adsorption test and with photoelectron spectroscopy , the d. of Ti atoms at the metal oxide/electrolyte interface decreased due to Al modification. There is not a complete coverage of Al oxide onto the TiO2 - the results suggest either the formation of a mixed Al-Ti oxide surface layer or formation of a partial Al oxide coating. No new phase was detected. In solar cells with Al-modified TiO2 electrodes electron lifetimes and electron transport times increased. At high concns. of inserted Al ions, the quantum efficiency for electron injection decreased. Results are discussed according to a multiple trapping model which can explain slower kinetics by the creation of addnl. traps during Al insertion, and a surface layer model which explains the reduced recombination rate as well as the reduced injection efficiency by the formation of a blocking layer.

Effects of Nb on the microstructure and corrosive property in the Alloy 690–SUS 304L weldment

A study of the microstructure and corrosion of dissimilar weldments of Alloy 690 and SUS 304L with various additions of niobium (Nb) (0.1, 1.03, 2.49, and 3.35% by weight) in the flux of coated electrodes is presented. With identical welding parameters and procedures, the weldments were butt-welded in three layers by shielding metal arc welding (SMAW), with each layer being deposited in a single pass. The results show that the dendritic microstructure in the fusion zone changed from a cellular to columnar dendrite and equiaxed dendrite with increasing Nb addition. Furthermore, the interdendritic phase increased in volume and changed in composition from an Al–Ti oxide to a mixture of Nb–Si phase and Nb-rich phase. Nevertheless, it was clearly observed that Cr 7C 3 precipitated at the grain boundaries of the low Nb weldment root pass. Finally, the results revealed that corrosion occurs primarily at the grain boundaries and within the interdendritic regions of the weldements irrespective of the level of Nb addition. For the region of abundant formation of Nb-rich phase, the high-Nb weldment had a relatively low corrosion resistance.

Characterization of Al-Ti oxide crystallites formed in corresponding gels by mechanical milling

Characterization of Al-Ti oxide crystallites formed in corresponding gels by mechanical milling

Al-Ti Oxide Crystallites Formed in Al2O3-TiO2 Gels by Mechanical Milling

Al-Ti Oxide Crystallites Formed in Al2O3-TiO2 Gels by Mechanical Milling

The role of titania in supported Mo, CoMo, NiMo, and NiW hydrodesulfurization catalysts: analysis of past and new evidences

Previous results and new evidence on the role of titania in supported hydrodesulfurization catalysts are analyzed in order to construct a rational explanation for the different findings in Ti-containing HDS catalysts. Some of the important findings follow. The preparation method of Al–Ti oxide supports is important to catalytic activity. It is not the total amount of Ti but the Ti oxide surface structures that is relevant. TiO 2 is an electronic promoter in HDS catalysts. Ti 3+ species formed under HDS reaction conditions act as electron donors. These electrons can be easily transferred, through the conduction band of the support, and be injected to the Mo 3d conduction band. This causes a weakening of the Mo S bonds and helps the creation of more CUS. The addition of TiO 2 to the surface of alumina eliminates the most reactive surface hydroxyl groups and avoids the formation of tetrahedral Mo oxide species, causing an increase of well-sulfided active phase and hence in catalytic activity. This effect, although significant, is less important than the electronic promotion of Mo by Ti. TiO 2-containing catalysts are well suited for deep HDS because they facilitate the formation of a greater number of CUS in MoS 2 (or WS 2), favoring the hydrogenation–hydrodesulfurization route of transformation of 4,6-DMDBT.

Dissimilar welding of nickel-based Alloy 690 to SUS 304L with Ti addition

This study investigates the effects of Ti addition on the weldability, microstructure and mechanical properties of a dissimilar weldment of Alloy 690 and SUS 304L. Shielding metal arc welding (SMAW) is employed to butt-weld two plates with three welding layers, where each layer is deposited in a single pass. To investigate the effects of Ti addition, the flux coatings of the electrodes used in the welding process are modified by varying additions of either a Ti–Fe compound or a Ti powder. The results indicate that the microstructure of the fusion zone (FZ) is primarily dendritic. With increasing Ti content, it is noted that the microstructure changes from a columnar dendritic to an equiaxed dendritic, in which the primary dendrite arm spacing (PDAS) becomes shorter. Furthermore, it is observed that the amount of Al–Ti oxide phase increases in the inter-dendritic region, while the amount of Nb-rich phase decreases. Moreover, the average hardness of the FZ increases slightly. The results indicate that Ti addition prompts a significant increase in the elongation of the weldment (i.e. 36.5%, Ti: 0.41 wt%), although the tensile strength remains relatively unchanged. However, at an increased Ti content of 0.91 wt%, an obvious reduction in the tensile strength is noted, which can be attributed to a general reduction in the weldability of the joint.

Intercalation of pseudo-boehmite: a novel preparation route to microporous Al–Ti oxide

Intercalation of titanium (IV) bislactato dihydroxide (TBLH) by noncrystalline pseudo-boehmite, AlOOH, was found to proceed successfully at room temperature by forming unidentate and bridging-type coordination of carboxylate groups to Al ions. The intercalation is likely driven by the partial substitution of TBLH for OH groups in the interlayer. Although the SEM observation indicated that the solids after heating at 300–500 °C were consisted of large grains of several micrometers in diameter, their surface areas were more than 300 m 2 g −1. The nitrogen adsorption/desorption isotherm and t-plot exhibit that the calcined product is basically microporous and no pores larger than 2 nm in radius are formed.

Nonstationary Phenomena in the Low-Temperature Gas-Phase Catalytic Oxidation of H2S with Oxygen

The conditions of the existence were determined and reasons were revealed for the appearance of periodic oscillations of the SO2concentration in the reaction products and warming temperature in the catalyst bed in the oxidation of H2S with oxygen at temperatures below the dew point of sulfur on the V–Al–Ti oxide catalyst. The formation of polysulfides during the reaction was experimentally found. It was proposed that the adsorption of sulfur and polysulfides on the catalyst surface is responsible for the observed oscillatory processes.